Kavli Affiliate: Tomotake Matsumura
| First 5 Authors: Thuong D. Hoang, Tomotake Matsumura, Ryota Takaku, Takashi Hasebe, Tommaso Ghigna
| Summary:
LiteBIRD is the Cosmic Microwave Background (CMB) radiation polarization
satellite mission led by ISAS/JAXA. The main scientific goal is to search for
primordial gravitational wave signals generated from the inflation epoch of the
Universe. LiteBIRD telescopes employ polarization modulation units (PMU) using
continuously rotating half-wave plates (HWP). The PMU is a crucial component to
reach unprecedented sensitivity by mitigating systematic effects, including 1/f
noise. We have developed a 1/10 scale prototype PMU of the LiteBIRD LFT, which
has a 5-layer achromatic HWP and a diameter of 50 mm, spanning the
observational frequency range of 34-161 GHz. The HWP is mounted on a
superconducting magnetic bearing (SMB) as a rotor and levitated by a
high-temperature superconductor as a stator. In this study, the entire PMU
system is cooled down to 10 K in the cryostat chamber by a 4-K Gifford-McMahon
(GM) cooler. We propagate an incident coherent millimeter-wave polarized signal
throughout the rotating HWP and detect the modulated signal. We study the
modulated optical signal and any rotational synchronous signals from the
rotation mechanism. We describe the testbed system and the preliminary data
acquired from this setup. This testbed is built to integrate the broadband HWP
PMU and evaluate the potential systematic effects in the optical data. This
way, we can plan with a full-scale model, which takes a long time for
preparation and testing.
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